Displaced Left-Turn (DLT) retrofit

#Applicability and thresholds

Requires substantial additional right-of-way width upstream of the main intersection to build the displaced left-turn crossing, which is this retrofit's primary limitation compared to Median U-Turn or RCUT.² Most viable at high-volume urban or suburban intersections where a grade-separated interchange isn't justified but conventional signal delay from protected left-turn phasing is severe.

#Evidence and effectiveness

DLT is documented as a faster, lower-cost alternative to a grade-separated interchange at high-volume intersections, resolving left-turn and through-movement conflicts without the cost of a flyover or underpass, though at higher construction cost and impact than Median U-Turn or RCUT.¹

#Getting it built

Cannot be piloted informally. Widening for the displaced left-turn crossing is real, costly construction, frequently impacting adjoining properties given the additional area required. This strategy effectively starts at Permanent on the construction spectrum. See Construction Methodology & The Build Spectrum.

An Intersection Control Evaluation is standard practice, and given the higher cost and impact of this design relative to Median U-Turn or RCUT, is particularly important for justifying the additional expense. See Decision & Evaluation Processes.

#Who can move this

Typically a state DOT or large-city capital project, given the cost and right-of-way scope involved. See Legal & Planning Mechanisms and Funding & Financing Mechanisms.